What the mutual admiration between Keir Starmer and Michel Barnier could mean for Brexit | Tom Baldwin

A curious feature of Brexiter psychology is how the ruinous outcome they once actively sought for Britain is now blamed on tricksy European negotiators, led at the time by Michel Barnier.

And so it was wearingly predictable that his re-emergence as the likely new French prime minister would produce a tide of their usual foam-flecked outrage. “We thought we’d seen the last of ‘Monsieur Barnier’ after the Brexit negotiations – where he was determined to get Britain the worst possible deal,” said the Tory MP John Hayes, even as the former cabinet minister Jacob Rees-Mogg declared that Barnier was “no friend of the UK”.

And, given that Liz Truss once suggested that “the jury is still out” on whether Emmanuel Macron is Britain’s “friend or foe”, the French president’s nomination of the former EU chief negotiator on Brexit to be PM was always going to provoke a particular hysteria. The Daily Telegraph gave Patrick O’Flynn (uber Brexiter, former Ukipper, ex-Farage lieutenant) a platform to unveil its “ proof that Macron loathes Britain ”.

Their fragile mental state will probably not be improved by hearing of the conversations I had with Starmer while writing his biography, about the years in which the last Tory government was regarded by the rest of Europe as having suffered some form of breakdown.

He described to me a feeling of embarrassment for Britain at the start of formal talks in 2017, when a fully prepped Barnier “turned up with a van load of papers in colour-coded ring binders, while David Davis [the then Brexit secretary] wandered in with nothing more than his glasses case ”.

As Davis’s opposite number, Starmer had met Barnier several times to explore detailed options for a “bespoke” form of customs union, during which their shared love of detail helped nurture some mutual respect between them. When I suggested it would be good for me to speak to Barnier, the Labour leader pulled out his phone, on which it just so happened that he still had a telephone number for him.

My book quotes from the resulting interview, in which the veteran centre-right French politician explained he had thought, even back then, that Starmer would one day become a centre-left prime minister of Britain. “He was always learning,” Barnier said. “He improved, day after day, year after year. While everyone else made mistakes, he was careful. From the first time we met, I thought there was something about him.”

In the years since, of course, Starmer has boxed himself in by ruling out not only rejoining the EU but also the customs union and the single market. There are plenty of critics, inside the Labour party and beyond, who think this is too cautious and careful.

Looking back at the notes of my chat with Barnier, however, there are clues about how the government can mitigate at least some of the damage being done.

Just as when Starmer was shadow Brexit secretary, there are two sets of red lines. The EU won’t accept any of what Barnier calls “cherry-picking”, and has apparently quashed a modest proposal from Britain to loosen post-Brexit curbs on UK touring musicians, while the government has swiftly rejected a Brussels scheme by which citizens under-30s could study and work in both the EU and UK as “free movement by the back door”. Although it should be possible to get progress on a deal to restrictions on trade in food and drink, that would inevitably prompt fresh hysteria about whether this once again makes Britain subject to rulings from European courts.

Barnier, while acknowledging there was limited room for improvements on such matters without a much bigger renegotiation, said the real opportunity lay in the original political declaration signed by Boris Johnson, which talked of deeper cooperation on defence and security. “If you look at what could be done by a Labour government, that part of the treaty is still open to negotiation.”

And this is precisely what lies behind Starmer’s “reset” of relations with European leaders that began shortly after the election at the Blenheim summit, where the prime minister emphasised the “blood bond of 1945” when Europe stood up to fascism. Russia’s war against Ukraine beyond the EU’s borders, as well as raging right populism within them, represent new, existential dangers to European liberal democratic values. So too, potentially, are threats ranging from terrorism and climate crisis to refugees and misinformation on digital platforms. As Barnier told me: “It would be better for the UK to tackle these problems together with the EU than to try to do so alone.”

Related: In picking Barnier, Macron has put his – and France’s – fate in Le Pen’s hands | Paul Taylor

There is already some momentum behind Britain’s efforts to secure a European security pact and David Lammy, the foreign secretary, is due to attend October’s summit, usually reserved for his EU counterparts. But the difficulty is to make this more than just a series of possibly tokenistic meetings. The government is keen, for instance, to secure closer cooperation with crime-fighting bodies on sharing data in tackling the people-trafficking gangs responsible for illegal immigration in small boats. Starmer also wants help from Macron – and perhaps now Barnier – in overcoming the self-interested opposition of the French defence industry to UK participation in EU-wide efforts to give Ukraine the weapons it needs.

Even such limited progress will not be easy. But Starmer has the advantage not only of having a respectful relationship with other European leaders: he also now leads a government that is a relative beacon of stability, in the context of months of political crisis that have paralysed France. Indeed, Barnier’s nomination has attracted even more fury from the left in his country than it has from the Brexiter right in this one.

For now, at least, Britain doesn’t seem such a basket case after all. Barnier, for one, will have noticed.

• Tom Baldwin is a journalist and author of Keir Starmer: The Biography